Question about a busted amp from a new guy.

[StilletoRay]

Hey guys,

I play through an old Peavey Mark VI stack at home that I bought a while back, and it has gone out on me. I have no experience with amp repair and am not much of a gear-head, and I need some advice on how to pinpoint the problem and hopefully fix it. Hopefully you fellas can help me out.

I don't think it's the cab, because I've never turned it up close to being loud enough to blow it. I guess it is possible, though because it's not exactly new.The head turns on fine, but hardly any signal is coming out of it. It sounds exactly like my bass sounds when the 9 volts are almost out of juice (there's nothing wrong with my bass. I've played through other amps and gigged with it this past weekend). The signal is just extremely weak, and the barely audible sound that is coming through sounds like a fart.

Thanks in advance to any responses,
Ben

[walterw]

test your cab by plugging a different amp into it. barring that, a 9V battery on the end of the speaker cable coming off the cab should make a loud thump when you touch the contacts to the tip and sleeve of the cable plug.

if the cab is still making sound, your head is blown. there's no home-fixing that, you'd need to take it to a tech.

[T-Bird]

Hi.


What walterw said.

IME Peaveys were a bit of a PITA to repair, at least over here across the pond, and their relative cheapness led to simply discarding them (or fitting an power amp module if that was blown).

By Your description, there's two likely culprits IME.

The more likely is a blown output section, the other is a "frozen" voice coil in the speaker. Neither is a job for a DIYer.

OTOH a rig that old, anything's possible, any tech can diagnose it way better than anyone over the keyboard.

Regards
Sam

[wave rider]

I have had the same problem with my Mark VI, it seems to be corroded or dirty preamp out and power amp in plugs on the front panel. I spray a little DeOxit™ into the plugin then plug in, slide, and twist around an instrument cable plug. For good measure, I do it to all the plugins. I think it is akin to a problem that many amps have with effects loop ins and outs. Agedhorse of Genz Benz had a good explanation somewhere...

That said, sometimes I have to fool with the pre and post gains up very high, and the signal will start to "force" itself through. After it "clears" itself, it sounds as great/powerful as always. Could be the capacitors or something else getting old...

Hope this helps,
=wr=

[Alex1984]

Contact cleaning is a good suggestion. +1 on testing different head/cab combinations to narrow down the problem. Outside of those possibilities, I'm afraid it's tech time.

[StilletoRay]

Thanks for the replies. I'll try that stuff out.